What is 0.1- in its simplified fraction

What are the domain and range of the function? f(x) = -4 (sqrt)x

Astudent must have an average on five test that is greater than it equal to 80% but less than 90% to receive a final grade of b. devon's greades on the first four test were 78% 62% 91% and 80% what range if grades on the fifth test would give him a b in the course? ( assuming the highest grade is 100%)

The function representing david's miles per month if f(m)= 115m + 5. what does the 115 represent